1. Field of the Invention
The present invention relates to a moving object image tracking apparatus and method for enabling a target recognition sensor, such as a camera, to track a target that can move in every direction.
2. Description of the Related Art
In recent years, systems for tracking an object using, for example, an ITV camera, to realize continued monitoring or acquire detailed information have been produced on a commercial basis for protective service equipment employed in major facilities such as airports and manufacturing plants, lifeline facilities such as electric power plants and water networks, and traffic information support systems such as ITSs. These systems include not only ground equipment type systems, but also compact ones installed in vehicles, ships or airplanes and having a vibration-proof structure. In the systems, it has come to be important to enhance their whirling speed to make them quickly point a plurality of targets and sequentially track the targets.
In the above moving object image tracking systems, the gimbal structure must have at least two axes to track a target that moves in every direction. In a biaxial gimbal, when the target passes the zenith or near the same, the AZ axis of the gimbal must instantly rotate through 180°. Actually, however, this motion is hard to realize, resulting in a gimbal lock phenomenon in which continuous tracking is impossible. Accordingly, the biaxial gimbal structure cannot be oriented to the zenith, which makes it difficult to realize omnidirectional tracking.
In the conventional moving object image tracking systems, the degree of freedom is increased using a triaxial gimbal structure, and one operation is distributed to the AZ axis and the xEL axis to prevent the angular velocity of the gimbal from excessively increasing, whereby the movable range of the gimbal is not exceeded to avoid the gimbal lock phenomenon and enable continuous omnidirectional tracking (see, for example, JP-A 2006-106910 (KOKAI)).
The above-described triaxial gimbal structure is more complex than the biaxial gimbal structure, and is hard to reduce in size and cost since it requires a larger number of driving means, such as motors. Further, since a camera, for example, is mounted on the gimbal structure, the load inertia of the xEL axis is large, which may cause axial interference between the AZ axis and the xEL axis. This is a problem peculiar to the triaxial gimbal structure.
Further, to execute tracking near the zenith using the biaxial gimbal structure, a motor performance that allows instant 180° rotation is required, for example. Thus, excessive requests must be satisfied.
The present invention has been developed in light of the above, and provides a moving object image tracking apparatus that exhibits improved tracking performance without any additional sensor, and a method employed therein.